Methacrylic resin composition

ABSTRACT

There is provided a heat-resistant methacrylic resin composition, which comprises 1 to 99% by weight of a copolymer [I] obtained by copolymerizing methyl methacrylate, an aromatic vinyl compound and maleic anhydride and 99 to 1% by weight of a copolymer [II] obtained by copolymerizing 80 to 100% by weight of methyl methacrylate and 0 to 20% by weight of other copolymerizable ethylenic monomer. 
     The resin composition according to the present invention is excellent in characteristics such as optical characteristics, mechanical properties, weathering resistance and molding processability as well as in productivity.

BACKGROUND OF THE INVENTION

This invention relates to a transparent heat-resistant methacrylic resin composition.

Methacrylic resins containing methyl methacrylate as the main component are very excellent in optical properties and weathering resistance, and also have relatively well-balanced performances in mechanical properties, thermal properties and molding processability. Therefore, by taking advantages of these characteristics, they are utilized widely in a large number of fields, including sign boards, covers for illumination, nameplates, automobile parts, parts of electrical instruments, decorative or miscellaneous goods. Further, developments for uses of these resins are also now under progress.

However, in one aspect, heat resistance is not sufficient with the heat distortion temperature being around 100° C., and there are a considerable number of fields for which developments of uses are limited. Thus, there continues to exist persistent demand for improvement of heat resistance.

There have been proposed a large number of methods for improvement of heat resistance of methacrylic resins, including, for example, the method in which methyl methacrylate is copolymerized with α-methylstyrene; the method in which methyl methacrylate, α-methylstyrene and maleic anhydride are copolymerized (Japanese Patent Publication No. 10156/1974); the method in which methyl methacrylate, styrene and maleic anhydride are copolymerized (Japanese Patent Publication No. 43242/1981); the method in which methyl methacrylate, α-methylstyrene, styrene and maleic anhydride are copolymerized (Japanese Provisional Patent Publication No. 81322/1981); the method in which poly-α-methylstyrene is dissolved in methyl methacrylate before polymerization of methyl methacrylate (Japanese Patent Publication Nos. 1616/1968 and 8718/1974); the method in which methyl methacrylate and N-allyl maleic acid imide are copolymerized (Japanese Patent Publication No. 9753/1968); the method in which methyl methacrylate, α-methylstyrene and maleimide are copolymerized; the method in which metyl methacrylate is copolymerized in the presence of a crosslinked polymer of a polyfunctional monomer; the method in which methyl methacrylate is copolymerized with methacrylic acid; the method in which methyl methacrylate, α-methylstyrene and acrylonitrile are copolymerized; and others. However, in the methods according to the proposals as mentioned above, polymerization rate may be extremely small to give markedly low productivity not acceptable in practical application; mechanical properties, weathering resistance and optical properties may be lowered; molded products may be markedly colored; or molding processability may be poor due to narrow molding region. Thus, in any case, under the present invention, while heat resistance may be improved to some extent, a number of problems remain to be solved.

SUMMARY OF THE INVENTION

The present inventors, in view of the state of the art as described above, have made extensive studies on a heat-resistant methacrylic resin without lowering excellent characteristics inherent in methyl methacrylate such as optical characteristics, mechanical properties, weathering resistance and molding processability, which is also excellent in productivity. Consequently, it has now been found that a resin mixture comprising a copolymer of methyl methacrylate, an aromatic vinyl compound and maleic anhydride having a specific composition and a methacrylic polymer can accomplish its object and has also an unexpected effect of being excellent in transparency in spite of the difference in refractive index between both of the resins. The present invention has been accomplished on the basis of such a finding.

More specifically, the resin composition of this invention comprises a copolymer [I] comprising methyl methacrylate, an aromatic vinyl compound and maleic anhydride and a (co)polymer [II] comprising 80 to 100% by weight of methyl methacrylate and 0 to 20% by weight of other ethylenic monomer copolymerizable therewith.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The most characteristic feature of the composition of this invention resides in that a composition excellent in weathering resistance and colorless transparency of molded products, further well-balanced in heat resistance, solvent resistance, mechanical properties and molding processability, as compared with the copolymers as disclosed in the above-cited Japanese Patent Publication Nos. 10156/1974 and 43242/1981, and Japanese Provisional Patent Publication No. 81322/1981, can unexpectedly be obtained by blending the above-mentioned heat resistant copolymer [I] having a specific composition with high refractive index and a resin constituted mainly of methyl methacrylate with low refractive index to effect homogeneous dispersion. Particularly, the salient feature of the composition according to this invention resides in the discovery that a resin composition providing a heat distortion temperature of 105° C. or higher, preferably 110° C. or higher, more preferably 115° C. or higher, can be obtained.

Methyl methacrylate constituting the copolymer [I] in the composition according to this invention is a component which maintains optical characteristics, weathering resistance or mechanical properties inherent in methacrylic resins and improves compatibility with the copolymer [II].

The aromatic vinyl compound which is a constituent of the copolymer [I] is selected from α-methylstyrene, styrene and vinyltoluene. α-Methylstyrene is a component for improving heat resistance and it is also a component for enhancing copolymerizing reactivity with maleic anhydride. Styrene or vinyltoluene is not a component for improving directly heat resistance, but it will improve heat resistance indirectly through enhancing copolymerizing reactivity with maleic anhydride and at the same time exhibits remarkable effect on improvement of productivity.

Maleic anhydride which is another constituent of the copolymer [I] is a component which improves heat resistance of the copolymer through the interaction with α-methylstyrene, styrene or vinyltoluene.

In the present invention, since the aromatic vinyl compound contstituting the copolymer [I] is selected from α-methylstyrene, styrene and vinyltoluene, the copolymer [I] can also take several kinds of compositions.

Copolymers [I] preferable for constituting the composition of this invention may include the following:

[A]: A copolymer comprising 50 to 98% by weight, preferably 65 to 90% by weight, of methyl methacrylate; and 1 to 25% by weight, preferably 5 to 18% by weight, of α-methylstyrene and 1 to 25% by weight, preferably 5 to 17% by weight of maleic anhydride.

[B]: A copolymer comprising 50 to 98% by weight, preferably 65 to 90% by weight; 1 to 25% by weight, preferably 5 to 20% by weight, of styrene or vinyl toluene; and 1 to 25% by weight, preferably 5 to 15% by weight of maleic anhydride.

[C]: A copolymer comprising 40 to 97% by weight, preferably 60 to 90% by weight of methyl methacrylate; 1 to 20% by weight, preferably 1 to 10% by weight of α-methylstyrene; 1 to 20% by weight, preferably 5 to 15% by weight of styrene or vinyltoluene; and 1 to 20% by weight, preferably 4 to 15% by weight of maleic anhydride.

In the composition of this invention, when the level of methyl methacrylate in the above copolymers [A], [B] and [C] constituting the copolymer [I] is less than the lower limit as specified above, maintenance of the optical properties, weathering resistance or mechanical properties inherent in methacrylic resins may be impaired, while at a level in excess of the upper limit, no improvement of heat resistance can be expected. On the other hand, if the level of α-methylstyrene is less than the lower limit, the resin will be inferior in productivity and heat resistance, while an excess over the upper limit will result in lowering of mechanical properties and optical properties and, further in resistance to thermal decomposition. As to styrene or vinyltoluene component, an insufficient level will cause indirectly lowering of heat resistance, while optical properties and weathering resistance will be lowered at an excessive level. Further, an insufficient amount of maleic anhydride will give only inferior results with respect to productivity and heat resistance, while an excessive amount will lower mechanical properties and optical properties, and further deteriorate the boiling resistance.

In the composition of this invention, when considering the resin properties of the finally obtained blended resin as a whole, such as heat resistance, mechanical properties, optical properties or molding processability, it is most preferred that the copolymer [I] should have a composition satisfying the quantitative relationship in terms of moles α of α-methylstyrene, moles β of styrene or vinyltoluene and moles γ of maleic anhydride so that the ratios of the respective components α/γ, β/γ, and (α+β)/γ may be in the range from 0.9 to 1.7. When these ratios are less than 0.9, water resistance and mechanical properties tend to be lowered. On the other hand, at ratios over 1.7, optical properties and heat resistance are observed to be lowered.

The copolymer [II] constituting the composition of this invention is added for the purpose of imparting weathering resistance, meahcnical properties, optical properties and molding processability inherent in methacrylic resins to the composition. The methyl methacrylate component which is the main component in the copolymer [II] is the component to impart weathering resistance, optical properties, heat resistance and mechanical properties inherent in methacrylic resins to the blended composition, and it may be used in the copolymer in an amount of 80 to 100% by weight. When the amount of methyl methacrylate employed is less than 80% by weight, the aforesaid physical properties tend to be lowered. Other ethylenic monomers to be used for copolymerization with methyl methacrylate may include acrylates of which alkyl moieties have 1 to 12 carbon atoms such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate and the like; methacrylates of which alkyl moieties have 2 to 12 carbon atoms such as ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate and the like, cyclohexyl methacrylate, styrene, acrlonitrile, and others. These monomers may be used singly or as a mixture of two or more kinds, in an amount ranging from 0 to 20% by weight.

The copolymer [I] and the copolymer [II] constituting the composition of this invention may be formulated at a proportion of 1 to 99% by weight of the copolymer [I] and a proportion of 99 to 1% by weight of the copolymer [II]. At a level lower than 1% by weight of the copolymer [I], heat resistance will be inferior, while mechanical properties and weathering resistance will be lowered at a level in excess of 99% by weight. On the other hand, when the amount of the copolymer [II] employed is less than 1% by weight, mechanical properties and weathering resistance will be inferior, while no improvement of heat resistance can be expected with a content over 99% by weight. Therefore, in the composition of this invention, when considering the balance between heat resistance, weathering resistance, coloration characteristic of molded articles, solvent resistance, mechanical properties and molding processability, the copolymer [I] should be 5 to 95% by weight and the copolymer [II] 95 to 5% by weight. Preferably, the copolymer [I] may be 10 to 90% by weight, more preferably 15 to 85% by weight, most preferably 20 to 80% by weight and, correspondingly, the copolymer [II] may preferably be 90 to 10% by weight, more preferably 85 to 15% by weight, most preferably 80 to 20% by weight.

The composition according to this invention is particularly useful as a molding material having a melt flow rate (MFR) of 0.5 to 75 (amount of resin (g) extruded as measured according to ASTM D-1238 under the condition of 230° C., under load of 10 Kg/cm² for 10 minutes).

The composition of this invention can be produced according to any method which is not particularly limited. For example, the copolymer [I] and the copolymer [II] may be prepared by bulk polymerization according to conventional methods, the copolymer [I] and the copolymer [II] obtained are blended and thereafter melt, kneaded and extruded at temperatures ranging from 200° to 300° C., to prepare a blended resin. Alternatively, the copolymer [I] is dissolved in a monomeric mixture for preparation of the copolymer [II], followed by suspension polymerization in an aqueous medium containing a dispersant or bulk polymerization. It is also possible to employ the method in which the copolymer [II] is dissolved in a monomeric mixture for constitution of the copolymer [I], followed by bulk polymerization of the mixture.

In the composition of this invention, there may also be added additives such as an UV-absorbers, peeling agents, antioxidants, mold release agents, dyes or pigments, if necessary.

The composition of this invention, which is excellent in heat resistance, weathering resistance, colorless transparency, boiling resistance and mechanical properties, is useful for lamps of automobiles, meter coverings, etc.

This invention is illustrated in more detail by referring to the following Examples.

Evaluations of the physical properties in Examples were conducted according to the methods shown below.

(1) Melt-flow property: MFR (melt-flow rate): ASTM D-1238, amount of resin extruded in grams, at 230° C., under load of 10 Kg/cm², for 10 minutes.

(2) Heat resistance: Heat distortion temperature (H.D.T.) (°C.): ASTM D-648

(3) Mechanical properties:

(1) Tensile strength (Kg/cm²): ASTM D-638

(2) Elongation (%): ASTM D-638

(4) Total light transmittance (%): ASTM D-1003

(5) Color tone of injection molded plate: Visual observation

(6) Weathering resistance: Accelerated exposure test, 1100 hours, Weather-o-meter produced by Suga Co., temperature: 60° C., carbon arc lamp, under rain fall for 12 minutes per hour.

(7) Boiling resistance: A test strip of 2 mm×50 mm×100 mm is immersed in pure water at 100° C. for 4 hours, and the degree of whitening is judged by visual observation.

(8) Solvent resistance: A stress of 4000 psi is applied on the fulcrum of a sample of a plate having a thickness of 2 mm, a width of 25 mm and a length of 110 mm, while wetting the fulcrum with isopropyl alcohol, and the time from commencement of measurement until development of craze or crack is measured.

EXAMPLE 1, COMPARATIVE EXAMPLES 1-3

To 1000 g of each of the monomeric mixtures containing methyl methacrylate, α-methylstyrene and maleic anhydride formulated at proportions as indicated in Table 1 was added 2.5 g of t-dodecyl mercaptan as a molecular weight controller, and the mixture was placed in a separable flask of 2-liter inner capacity equipped with a condenser, a thermometer and a stirrer. Then, under stirring, nitrogen gas was blown into the flask to purge the air in the system, and on heating the mixture to 70° C., 0.2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) was added thereto, and the inner temperature was maintained at 95° C. for 15 minutes, followed by cooling to room temperature, to obtain a partially polymerized product.

To 1,000 g of the partially polymerized product were added and dissolved therein under thorough stirring 4 g of lauroyl peroxide, 3.0 g of t-dodecyl mercaptan as molecular weight controller, 0.3 g of "Tinuvin P" (trade name, produced by Ciba-Geigy AG) as an UV-absorber, 0.2 g of "JP-504" (trade name: produced by Johoku Kagaku Co.) as a peeling agent, 1 g of "Mark 329" (trade name: produced by Adeka Argus Co.) as a stabilizer and 1 g of stearic acid monoglyceride as a mold release agent. This partially polymerized mixture was poured into a mold comprising a cell formed of two tempered glass plates placed at a distance of 3 mm through an intermediary polyvinyl chloride gasket, which cell was equipped with a thermocouple, and curing by polymerization was conducted in a water bath at 80° C. Thirty minutes after confirmation of the time from immersion in the water bath until the inner temperature reaches its peak, the mold was taken out from the water bath and subjected to heat treatment in an air-heated furnace at 130° C. for 2 hours. After cooling, the glass plates were removed to obtain a resin plate with a plate thickness of about 3 mm. The plate was cut and crushed into pellets of about 3 to 4 mm.

                  TABLE 1                                                          ______________________________________                                                 Composition of monomeric mixture (g)                                                      α-methyl-                                                                           Maleic                                                   Methyl metha-                                                                             styrene    anhydride                                                crylate (MMA)                                                                             (α-MeSt)                                                                            (MAH)                                            ______________________________________                                         Example 1 700          160        140                                          Comparative                                                                              800          200        --                                           example 1                                                                      Comparative                                                                              800          --         200                                          example 2                                                                      Comparative                                                                              --           520        480                                          example 3                                                                      ______________________________________                                    

These pellets were blended with a methacrylic polymer [Acrypet (registered trade name) VH, produced by Mitsubishi Rayon Co.] at a weight ratio of 60/40 and molded into pellets at 200° to 270° C. by means of a vent type biaxial extruder (extrusion temperature: 270° C.).

These pellets were injection molded under the conditions shown below, and the test strips obtained (110 mm×110 mm×2 mm thick) were evaluated to obtain the results shown in Table 2.

Injection molding machine: V-17-65 Model screw type automatic injection molding machine, produced by Nippon Seikosho Co.

Injection molding conditions:

Cylinder temperature: 250°-260° C.

Injection pressure: 700 Kg/cm²

Mold temperature: 50° C.

                  TABLE 2                                                          ______________________________________                                                           Compara-  Compara- Compara-                                  Evaluation                                                                              Exam-    tive      tive     tive                                      item     ple 1    example 1 example 2                                                                               example 3                                 ______________________________________                                         MFR      8.0      8.0       not measur-                                                                             12.0                                      (g/10 min.)                 ed       because                                   H.D.T. (°C.)                                                                     116      104       MMA/MAH  114                                       Tensile  770      770       were not 600                                       strength                    copoly-                                            (Kg/cm.sup.2)               merized                                            Elongation                                                                              4.0      3.0                1.9                                       (%)                                                                            Total light                                                                             92       30                 <20                                       transmit-                                                                               tance (%)                                                             Color tone                                                                              color-   semi-              yellow                                    of injec-                                                                               less     trans-             semi-                                     tion molded                                                                             trans-   parent             trans-                                    plate    parent                      parent                                    Weathering                                                                              no       no                 craze,                                    resistance                                                                              change   change             crack                                     (acceler-                            generated                                 ated exposure                                                                  test, 1100                                                                     hours)                                                                         Boiling  not      not                whitened                                  resistance                                                                              whitened whitened                                                     Solvent  200      210                80                                        resistance                                                                     (sec.)                                                                         ______________________________________                                    

EXAMPLES 2-3, COMPARATIVE EXAMPLES 4-5

The procedure of Example 1 was repeated, except for changing the compositions of methyl methacrylate, α-methylstyrene and maleic anhydride as indicated in Table 3 and the blend ratio relative to the methacrylic resin to 80/20, to prepare resin compositions. The evaluation results obtained are shown in Table 4.

                  TABLE 3                                                          ______________________________________                                                Composition of monomeric mixture (g)                                                      α-methyl-                                                     Methyl metha-                                                                             strene    Maleic                                                    crylate (MMA)                                                                             (α-MeSt)                                                                           anhydride (MAH)                                    ______________________________________                                         Comparative                                                                             700          300        0                                             example 4                                                                      Example 2                                                                               "            240        60                                            Example 3                                                                               "            150       150                                            Example 4                                                                               "             60       240                                            Comparative                                                                             "             0        300                                            example 5                                                                      ______________________________________                                    

                  TABLE 4                                                          ______________________________________                                                  Compara-                      Compara-                                Evaluation                                                                              tive      Exam-   Exam- Exam- tive                                    item     example 4 ple 2   ple 3 ple 4 Example 5                               ______________________________________                                         MFR      not mea-  15.6    11.0  9.0   6.2                                     (g/10 min.)                                                                             sured                                                                 H.D.T. (°C.)                                                                     because   112     118   110   102                                     Tensile  MMA-α-                                                                             700     710   730   740                                     strength MeSt                                                                  (Kg/cm.sup.2)                                                                           were not                                                              Elongation                                                                              solidi-   3.7     3.8   4.8   7.5                                     (%)      fied but                                                              Total light                                                                             became    91      91.5  92    90.5                                    transmit-                                                                               syrupy                                                                tance (%)                                                                      Color tone         color-  color-                                                                               color-                                                                               color-                                  of injec-          less    less  less  less                                    tion molded        trans-  trans-                                                                               trans-                                                                               trans-                                  plate              parent  parent                                                                               parent                                                                               parent                                  Weathering         no      no    no    craze                                   resistance         change  change                                                                               change                                                                               generated                               (acceler-                                                                      ated exposure                                                                  test, 1100                                                                     hours)                                                                         Boiling            not     not   slightly                                                                             whitened                                resistance         whit-   whit- whit-                                                            ened    ened  ened                                          Solvent            120     140   110   30                                      resistance                                                                     (sec.)                                                                         ______________________________________                                    

EXAMPLES 5-6, COMPARATIVE EXAMPLES 6-9

Copolymers were prepared in the same manner as in Example 1 from each 1000 g of monomeric mixtures with formulations of methyl methacrylate, α-methylstyrene and maleic anhydride as shown in Table 5, and three kinds of plates of 6 mm thickness were obtained therefrom. These plates were cut, crushed and molded by means of a vent type extruder into pellets.

                  TABLE 5                                                          ______________________________________                                                   Composition of monomeric mixture (g)                                 ______________________________________                                         Copolymer A MMA/α-MeSt/MAH = 796/114/90                                  Copolymer B MMA/α-MeSt/MAH = 670/180/150                                 Copolymer C MMA/α-MeSt/MAH = 350/350/300                                 ______________________________________                                    

These pellets were blended with the same methacrylic resin as employed in Example 1 as indicated in Table 6, followed by injection molding, and the physical properties of the molded products were evaluated to obtain the results as shown in Table 6.

                                      TABLE 6                                      __________________________________________________________________________                          Results of evaluation                                                              Total                                                                          light Tensile      Weath-                                                                              Boil-                                                                             Solvent                                    Blend    trans-                                                                               strength                                                                            Elon-   ering                                                                               ing                                                                               resis-                     Copoly-    Copoly-                                                                             ratio*                                                                              H.D.T.                                                                             mit-  (Kg/ gation                                                                             Color                                                                              resis-                                                                              resis-                                                                            tance                      mer [I]    mer [II]                                                                            (weight)                                                                            (°C.)                                                                       tance (%)                                                                            cm.sup.2)                                                                           (%) tone**                                                                             tance***                                                                            tance                                                                             (sec.)                     __________________________________________________________________________     Compara-                                                                             Copoly-                                                                             Meth-                                                                               100/0                                                                               112 92    700  3.0 pale                                                                               colored                                                                             not                                                                               100                        tive  mer (A)                                                                             acrylic                      yellow                                                                             in   whit-                         example 6  copoly-                      trans-                                                                             yellow                                                                              ened                                     mer                          parent                                 Example 5                                                                            Copoly-                                                                             Meth-                                                                               90/10                                                                               110 92    710  3.3 color-                                                                             no   not                                                                               130                              mer (A)                                                                             acrylic                      less                                                                               change                                                                              whit-                                    copoly-                      trans-   ened                                     mer                          parent                                 Compara-                                                                             Copoly-                                                                             Meth-                                                                               100/0                                                                               125 92    680  2.8 yellow                                                                             yellow-                                                                             not                                                                                85                        tive  mer (B)                                                                             acrylic                      trans-                                                                             ish  whit-                         example 7  copoly-                      parent                                                                             brown                                                                               ened                                     mer                                                                 Example 6                                                                            Copoly-                                                                             Meth-                                                                               75/25                                                                               120   90.5                                                                               720  4.0 color-                                                                             no   not                                                                               135                              mer (B)                                                                             acrylic                      less                                                                               change                                                                              whit-                                    copoly-                      trans-   ened                                     mer                          parent                                 Compara-                                                                             Copoly-                                                                             Meth-                                                                               100/0                                                                               122 opaque                                                                               600  1.1 pearly                                                                             craze                                                                               whit-                                                                              40                        tive  mer (C)                                                                             acrylic                      turbid                                                                             gen- ened                          example 8  copoly-                          erated                                        mer                                                                 Compara-                                                                             Copoly-                                                                             Meth-                                                                               75/25                                                                               118 opaque                                                                               630  1.7 pearly                                                                             yellow-                                                                             whit-                                                                              70                        tive  mer (C)                                                                             acrylic                      turbid                                                                             ish  ened                          example 9  copoly-                          milky                                         mer                                                                 __________________________________________________________________________      *Copolymer [I]/Copolymer [II],                                                 **Color tone of injection molded plate                                         ***Accelerated exposure test, 1100 hours                                 

EXAMPLES 7-11, COMPARATIVE EXAMPLES 10-11

A monomeric mixture of 645 g of methyl methacrylate, 190 g of α-methylstyrene and 165 g of maleic anhydride was polymerized according to the same procedure as in Example 1, except for changing the amount of t-dodecyl mercaptan during partial polymerization to 3.5 g and the amount of t-dodecyl mercaptan during plate formation to 4.0 g, to prepare a plate-shaped copolymer with a thickness of 3 mm. This copolymer was cut, crushed and blended with the methacrylic polymer of Example 1 at the proportions shown in Table 7, followed by extrusion molding into pellets by means of a biaxial extruder at 250 r.p.m. at 260° C. The pellets were then injection molded into test strips, which were evaluated to obtain the results shown in Table 8.

                  TABLE 7                                                          ______________________________________                                                Copolymer of MMA/α-                                                                     Methacrylic polymer                                             MeSt/MAH (g)   (Acrypet VH) (g)                                         ______________________________________                                         Comparative                                                                             1000              0                                                   example 10                                                                     Example 7                                                                               875              125                                                  Example 8                                                                               750              250                                                  Example 9                                                                               500              500                                                  Example 10                                                                              250              750                                                  Example 11                                                                              125              875                                                  Comparative                                                                              0               1000                                                 example 11                                                                     ______________________________________                                    

                                      TABLE 8                                      __________________________________________________________________________            Compara-                  Compara-                                      Evaluation                                                                            tive  Exam-                                                                              Exam-                                                                              Exam-                                                                              Exam-                                                                              Exam-                                                                              tive                                          item   example 10                                                                           ple 7                                                                              ple 8                                                                              ple 9                                                                              ple 10                                                                             ple 11                                                                             example 11                                    __________________________________________________________________________     H.D.T. (°C.)                                                                   129   124 119 113 109 106 102                                           Total light                                                                            92    92  92  92  92  92  93                                           transmit-                                                                      tance (%)                                                                      Tensile                                                                               650   670 720 740 780 790 790                                           strength                                                                       (Kg/cm.sup.2)                                                                  Elongation                                                                            2.5   3.0 3.3 4.5 6.8 7.0 7.2                                           (%)                                                                            Color tone                                                                            yellow                                                                               color-                                                                             color-                                                                             color-                                                                             color-                                                                             color-                                                                             color-                                        of injec-                                                                             trans-                                                                               less                                                                               less                                                                               less                                                                               less                                                                               less                                                                               less                                          tion molded                                                                           parent                                                                               trans-                                                                             trans-                                                                             trans-                                                                             trans-                                                                             trans-                                                                             trans-                                        plate        parent                                                                             parent                                                                             parent                                                                             parent                                                                             parent                                                                             parent                                        Weathering                                                                            yellow-                                                                              pale                                                                               no  no  no  no  no                                            resistance                                                                            ish   yellow                                                                             change                                                                             change                                                                             change                                                                             change                                                                             change                                        (acceler-                                                                             brown                                                                   ated exposure                                                                  test, 1100                                                                     hours)                                                                         Boiling                                                                               whit-     not not not not not                                           resistance                                                                            ened      whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                          ened                                                                               ened                                                                               ened                                                                               ened                                                                               ened                                          Solvent                                                                                45       120 160 200 230 250                                           resistance                                                                     (sec.)                                                                         __________________________________________________________________________

EXAMPLES 12-13, COMPARATIVE EXAMPLES 12-14

To 1000 g of each of the monomeric mixtures containing methyl methacrylate, styrene and maleic anhydride formulated at proportions as indicated in Table 9 was added 2.5 g of t-dodecyl mercaptan as a molecular weight controller, and the mixture was placed in a separable flask of 2-liter inner capacity equipped with a condenser, a thermometer and a stirrer. Then, under stirring, nitrogen gas was blown into the flask to purge the air in the system, and on heating the mixture to 70° C., 0.2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) was added thereto, and the inner temperature was maintained at 95° C. for 15 minutes, followed by cooling to room temperature, to obtain a partially polymerized product.

To 1,000 g of the partially polymerized product were added and dissolved therein under thorough stirring 4 g of lauroyl peroxide, 3.0 g of t-dodecyl meracptan as a molecular weight controller, 0.3 g of "Tinuvin P" (trade name, produced by Ciba-Geigy AG) as an UV-absorber, 0.2 g of "JP-504" (trade name: produced by Johoku Kagaku Co.) as a peeling agent, 1 g of "Mark 329" (trade name: produced by Adeka Argus Co.) as a stabilizer and 1 g of stearic acid monoglyceride as a mold release agent. This partially polymerized mixture was poured into a mold comprising a cell formed of two tempered glass plates placed at a distance of 3 mm through an intermediary polyvinyl chloride gasket, which cell was equipped with a thermocouple, and curing by polymerization was conducted in a water bath at 80° C. Thirty minutes after confirmation of the time from immersion in the water bath until the inner temperature reaches its peak, the mold was taken out from the water bath and subjected to heat treatment in an air-heated furnace at 130° C. for 2 hours. After cooling, the glass plates were removed to obtain a resin plate with a plate thickness of about 3 mm. The plate was cut and crushed into pellets of about 3 to 4 mm.

                  TABLE 9                                                          ______________________________________                                                Composition of monomeric mixture (g)                                           Methyl                                                                         metha-            p-Methyl  Maleic                                             crylate  Styrene  styrene   anhydride                                          (MMA)    (St)     (P-MS)    (MAH)                                       ______________________________________                                         Example 12                                                                              740        140              120                                       Comparative                                                                             800        200                                                        example 12                                                                     Comparative                                                                             800                         200                                       example 13                                                                     Comparative         515              485                                       example 14                                                                     Example 13                                                                              740                 140     120                                       ______________________________________                                    

These pellets were blended with a methacrylic polymer [Acrypet (registered trade name) VH, produced by Mitsubishi Rayon Co.] at a weight ratio of 60/40 and molded into pellets at 200° to 270° C. by means of a vent type biaxial extruder (extrusion temperature: 270° C.).

These pellets were injection molded under the conditions shown below, and the test strips obtained (110 mm×110 mm×2 mm thick) were evaluated to obtain the results shown in Table 10.

Injection molding machine: V-17-65 Model screw type automatic injection molding machine, produced by Nippon Seikosho Co.

Injection molding conditions:

Cylinder temperature: 250°-260° C.

Injection presure: 700 Kg/cm²

Mold temperature: 60° C.

                  TABLE 10                                                         ______________________________________                                                           Compar-  Compar-                                                                               Compar-                                                        ative    ative  ative                                        Evaluation                                                                               Exam-   example  example                                                                               example                                                                               Exam-                                 item      ple 12  12       13     14     ple 13                                ______________________________________                                         MFR       8.5     8.0      not    12.0   8.0                                   (g/10 min.,                mea-                                                230° C., 10 Kg)     sured                                               H.D.T. (°C.)                                                                      110     99       because                                                                               111    111                                   Tensile   770     710      MMA/   540    760                                   strength                   MAH                                                 (Kg/cm.sup.2)              were                                                Elongation                                                                               4.5     3.2      not    1.7    4.2                                   (%)                        copoly-                                             Total light                                                                              92      30       merized                                                                               20>    92                                    transmit- tance (%)                                                            Color tone                                                                               color-  semi-           colored                                                                               color-                                of injec- less    trans-          in     less                                  tion molded                                                                              trans-  parent          yellow trans-                                plate     parent                  opaque parent                                Weathering                                                                               no      no              craze, no                                    resistance                                                                               change  change          crack  change                                (acceler-                         gener-                                       ated exposure                     ated                                         test, 1100                                                                     hours)                                                                         Boiling   not     not             whit-  not                                   resistance                                                                               whit-   whit-           ened   whit-                                           ened    ened                   ened                                  Solvent   190     140             60     170                                   resistance                                                                     (sec.)                                                                         ______________________________________                                    

EXAMPLES 14-16, COMPARATIVE EXAMPLES 15-16

The procedure of Example 13 was repeated, except for changing the compositions of methyl methacrylate, styrene and maleic anhydride as indicated in Table 11 and the blend ratio relative to the methacrylic resin to 80/20, to prepare resin compositions. The evaluation results obtained are shown in Table 12.

                  TABLE 11                                                         ______________________________________                                                Composition of monomeric mixture (g)                                           Methyl metha-                                                                             Styrene  Maleic                                                     crylate (MMA)                                                                             (St)     anhydride (MAH)                                     ______________________________________                                         Comparative                                                                             700          300       0                                              example 15                                                                     Example 14                                                                              "            240       60                                             Example 15                                                                              "            150      150                                             Example 16                                                                              "             60      240                                             Comparative                                                                             "             0       300                                             example 16                                                                     ______________________________________                                    

                  TABLE 12                                                         ______________________________________                                                  Compara-                      Compara-                                Evaluation                                                                              tive      Exam-   Exam- Exam- tive                                    item     example 15                                                                               ple 14  ple 15                                                                               ple 16                                                                               example 16                              ______________________________________                                         MFR      19.0      17.0    13.0  10.5  8.5                                     (g/10 min.)                                                                    H.D.T. (°C.)                                                                     98        107     112   108   102                                     Tensile  680       700     700   700   710                                     strength                                                                       (Kg/cm.sup.2)                                                                  Elongation                                                                              2.5       3.4     3.6   4.2   7.5                                     (%)                                                                            Total light                                                                             70        92      90.5  92    90.5                                    transmit-                                                                      tance (%)                                                                      Color tone                                                                              milky     color-  color-                                                                               color-                                                                               color-                                  of injec-                                                                               white     less    less  less  less                                    tion molded                                                                             semi-     trans-  trans-                                                                               trans-                                                                               trans-                                  plate    trans-    parent  parent                                                                               parent                                                                               parent                                           parent                                                                Weathering                                                                              craze     no      no    no    craze                                   resistance                                                                              gener-    change  change                                                                               change                                                                               generated                               (acceler-                                                                               ated                                                                  ated exposure                                                                  test, 1100                                                                     hours)                                                                         Boiling  not       not     not   slightly                                                                             whitened                                resistance                                                                              whit-     whit-   whit- whit-                                                  ened      ened    ened  ened                                          Solvent  100       110     130   105   30                                      resistance                                                                     (sec.)                                                                         ______________________________________                                    

EXAMPLES 17, COMPARATIVE EXAMPLES 17-19

Copolymers were prepared in the same manner as in Example 1 from each 1000 g of monomeric mixtures with formulations of methyl methacrylate, styrene and maleic anhydride as shown in Table 13, and plates of 6 mm thickness were obtained therefrom. These plates were cut, crushed and molded similarly as in Example 12 by means of an extruder into pellets.

                  TABLE 13                                                         ______________________________________                                                   Composition of monomeric mixture (g)                                 ______________________________________                                         Copolymer (A)                                                                              MMA/St/MAH = 670/180/150                                           Copolymer (B)                                                                              MMA/St/MAH = 350/350/300                                           ______________________________________                                    

These pellets were blended with the same methacrylic resin as employed in Example 12 as indicated in Table 14, followed by injection molding, and the physical properties of the molded products were evaluated to obtain the results as shown in Table 14.

                                      TABLE 14                                     __________________________________________________________________________                          Results of evaluation                                                     Blend    Total                                                                 ratio    light Tensile       Weath-                                                                              Boil-                                                                             Solvent                                   (weight) trans-                                                                               strength                                                                            Elon-    ering                                                                               ing                                                                               resis-                    Copoly-    Copoly-                                                                             [I]/ H.D.T.                                                                             mit-  (Kg/ gation                                                                             Color                                                                               resis-                                                                              resis-                                                                            tance                     mer [I]    mer [II]                                                                            [II] (°C.)                                                                       tance (%)                                                                            cm.sup.2)                                                                           (%) tone*                                                                               tance**                                                                             tance                                                                             (sec.)                    __________________________________________________________________________     Compara-                                                                             Copoly-                                                                             Meth-                                                                               100/0                                                                               120 92    700  2.8 colored                                                                             yellow-                                                                             not                                                                               65                        tive  mer (A)                                                                             acrylic                      in   ish  whit-                        example 17 copoly-                      yellow                                                                              brown                                                                               ened                                    mer                          trans-                                                                         parent                                 Example 17                                                                           Copoly-                                                                             Meth-                                                                               75/25                                                                               115 91    720  3.9 color-                                                                              no   not                                                                               100                             mer (A)                                                                             acrylic                      less change                                                                              whit-                                   copoly-                      trans-    ened                                    mer                          parent                                 Compara-                                                                             Copoly-                                                                             Meth-                                                                               100/0                                                                               122 opaque                                                                               600  1.1 pearly                                                                              craze                                                                               whit-                                                                             30                        tive  mer B                                                                               acrylic                      turbid                                                                              gen- ened                         example 18 copoly-                           erated                                       mer                                                                 Compara-                                                                             Copoly-                                                                             Meth-                                                                               75/25                                                                               116 opaque                                                                               630  1.9 pearly                                                                              craze                                                                                --                          tive  mer B                                                                               acrylic                      turbid                                                                              gen-                              example 19 copoly-                           erated                                       mer                                                                 __________________________________________________________________________      *Color tone of injection molded plate                                          **Accelerated exposure test, 1100 hours                                  

EXAMPLES 18-22, COMPARATIVE EXAMPLES 20-21

A monomeric mixture of 700 g of methyl methacrylate, 160 g of styrene and 140 g of maleic anhydride was polymerized according to the same procedure as in Example 12 to prepare a plate-shaped copolymer with a thickness of 3 mm. This copolymer was cut, crushed and blended with the methacrylic polymer of Example 12 at the proportions shown in Table 15, followed by extrusion molding into pellets by means of a biaxial extruder at 250 r.p.m. at 260° C. The pellets were then injection molded into test strips, which were evaluated to obtain the results shown in Table 16.

                  TABLE 15                                                         ______________________________________                                                Copolymer of MMA/St/                                                                          Methacrylic polymer                                             MAH (g)        (Acrypet VH) (g)                                         ______________________________________                                         Comparative                                                                             1000              0                                                   example 20                                                                     Example 18                                                                              875              125                                                  Example 19                                                                              750              250                                                  Example 20                                                                              500              500                                                  Example 21                                                                              250              750                                                  Example 22                                                                              125              875                                                  Comparative                                                                              0               1000                                                 example 21                                                                     ______________________________________                                    

                                      TABLE 16                                     __________________________________________________________________________            Compara-                  Compara-                                      Evaluation                                                                            tive  Exam-                                                                              Exam-                                                                              Exam-                                                                              Exam-                                                                              Exam-                                                                              tive                                          item   example 20                                                                           ple 18                                                                             ple 19                                                                             ple 20                                                                             ple 21                                                                             ple 22                                                                             example 21                                    __________________________________________________________________________     H.D.T. (°C.)                                                                   121   118 116 111 107 105 102                                           Total light                                                                            92    92  92  92  92  92  93                                           transmit-                                                                      tance (%)                                                                      Tensile                                                                               700   710 720 740 780 780 790                                           strength                                                                       (Kg/cm.sup.2)                                                                  Elongation                                                                            2.6   3.2 3.6 4.8 6.8 7.0 7.2                                           (%)                                                                            Color tone                                                                            pale  color-                                                                             color-                                                                             color-                                                                             color-                                                                             color-                                                                             color-                                        of injec-                                                                             yellow                                                                               less                                                                               less                                                                               less                                                                               less                                                                               less                                                                               less                                          tion molded                                                                           trans-                                                                               trans-                                                                             trans-                                                                             trans-                                                                             trans-                                                                             trans-                                                                             trans-                                        plate  parent                                                                               parent                                                                             parent                                                                             parent                                                                             parent                                                                             parent                                                                             parent                                        Weathering                                                                            colored                                                                              slight-                                                                            no  no  no  no  no                                            resistance                                                                            in    ly pale                                                                            change                                                                             change                                                                             change                                                                             change                                                                             change                                        (acceler-                                                                             yellow                                                                               yellow                                                            ated exposure                                                                  test, 1100                                                                     hours)                                                                         Boiling                                                                               whit- not not not not not not                                           resistance                                                                            ened  whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                      ened                                                                               ened                                                                               ened                                                                               ened                                                                               ened                                                                               ened                                          Solvent                                                                                55   105 130 170 210 240 250                                           resistance                                                                     (sec.)                                                                         __________________________________________________________________________

EXAMPLES 23-27, COMPARATIVE EXAMPLES 22-23

To 1000 g of a monomeric mixture containing 650 g of methyl methacrylate, 50 g of α-methylstyrene, 150 g of styrene and 150 g of maleic anhydride was added 3.5 g of t-dodecyl mercaptan as a molecular weight controller, and the mixture was placed in a separable flask of 2-liter inner capacity equipped with a condenser, a thermometer and a stirrer. Then, under stirring, nitrogen gas was blown into the flask to purge the air in the system, and on heating the mixture to 70° C., 0.2 g of azobisisobutyronitrile as a polymerization initiator was added thereto, and the inner temperature was maintained at 95° C. for 15 minutes, followed by cooling to room temperature, to obtain a partially polymerized product of 600 centipoise.

To 1,000 g of the partially polymerized product were added and dissolved therein under thorough stirring 4 g of lauroyl peroxide, 3.0 g of t-dodecyl meracptan as a molecular weight controller, 0.2 g of "JP-504" (trade name, produced by Johoku Kagaku Co.) as a peeling agent, 0.3 g of "Tinuvin P" (trade name: produced by Ciba-Geigy AG) as an UV-absorber, 1 g of "Mark 329" (trade name: produced by Adeka Argus Co.) as a stabilizer and 1 g of stearic acid monoglyceride as a mold release agent. This partially polymerized mixture was poured into a mold comprising a cell formed of two tempered glass plates place at a distance of 3 mm through an intermediary polyvinyl chloride gasket, which cell was equipped with a thermocouple, and curing by polymerization was conducted in a water bath at 80° C. Thirty minutes after confirmation of the time from immersion in the water bath until the inner temperature reaches its peak, the mold was taken out from the water bath and subjected to heat treatment in an air-heated furnace at 130° C. for 2 hours. After cooling, the glass plates were removed to obtain a resin plate with a plate thickness of about 3 mm. The plate was cut and crushed into pellets of about 3 to 4 mm. These pellets were blended by a Henshell mixer with a methacrylic polymer "Acrypet (registered trade name) VH" (produced by Mitsubishi Rayon Co.) at the weight ratios as indicated in Table 17 and molded into pellets by means of a vent type biaxial extruder at a temperature of 265° C.).

These pellets were injection molded under the conditions shown below, and the test strips obtained (110 mm×110 mm×2 mm thick) were evaluated to obtain the results shown in Table 18.

Injection molding machine: V-17-65 Model screw type automatic injection molding machine, produced by Nippon Seikosho Co.

Injection molding conditions:

Cylinder temperature: 250°-260° C.

Injection presure: 700 Kg/cm²

Mold temperature: 60° C.

                  TABLE 17                                                         ______________________________________                                                 Copolymer of MMA/ -                                                            MeSt/St/MAH   Methacrylic polymer                                              copolymer     (Acrypet VH) (g)                                         ______________________________________                                         Comparative                                                                              1000             0                                                   example 22                                                                     Example 23                                                                               875             125                                                  Example 24                                                                               750             250                                                  Example 25                                                                               500             500                                                  Example 26                                                                               250             750                                                  Example 27                                                                               125             875                                                  Comparative                                                                               0              1000                                                 example 23                                                                     ______________________________________                                    

                                      TABLE 18                                     __________________________________________________________________________            Compara-                  Compara-                                      Evaluation                                                                            tive  Exam-                                                                              Exam-                                                                              Exam-                                                                              Exam-                                                                              Exam-                                                                              tive                                          item   example 22                                                                           ple 23                                                                             ple 24                                                                             ple 25                                                                             ple 26                                                                             ple 27                                                                             example 23                                    __________________________________________________________________________     H.D.T. (°C.)                                                                   128   124 121 115 109 106 102                                           Total light                                                                            92    92  92  92  92  92  93                                           transmit-                                                                      tance (%)                                                                      Tensile                                                                               720   730 750 770 780 790 790                                           strength                                                                       (Kg/cm.sup.2)                                                                  Elongation                                                                            2.7   3.3 4.0 5.0 6.9 7.0 7.2                                           (%)                                                                            Color tone                                                                            pale  color-                                                                             color-                                                                             color-                                                                             color-                                                                             color-                                                                             color-                                        of injec-                                                                             yellow                                                                               less                                                                               less                                                                               less                                                                               less                                                                               less                                                                               less                                          tion molded                                                                           trans-                                                                               trans-                                                                             trans-                                                                             trans-                                                                             trans-                                                                             trans-                                                                             trans-                                        plate  parent                                                                               parent                                                                             parent                                                                             parent                                                                             parent                                                                             parent                                                                             parent                                        Weathering                                                                            yellow                                                                               slight-                                                                            no  no  no  no  no                                            resistance   ly pale                                                                            change                                                                             change                                                                             change                                                                             change                                                                             change                                        (acceler-    yellow                                                            ated exposure                                                                  test, 1100                                                                     hours)                                                                         Boiling                                                                               whit- not not not not not not                                           resistance                                                                            ened  whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                                              whit-                                                      ened                                                                               ened                                                                               ened                                                                               ened                                                                               ened                                                                               ened                                          Solvent                                                                                65   110 140 160 210 230 250                                           resistance                                                                     (sec.)                                                                         __________________________________________________________________________

EXAMPLES 28-31, COMPARATIVE EXAMPLES 24

To each 1000 g of the monomeric mixtures containing methyl methacrylate, α-methylstyrene, styrene and maleic anhydride formulated at proportions as indicated in Table 19 was added 2.6 g of t-dodecyl mercaptan as a molecular weight controller, and the mixture was placed in a 2-liter separable flask equipped with a condenser, a thermometer and a stirrer. Then, under stirring, nitrogen gas was blown into the flask to purge the air in the system, and on heating the mixture to 70° C., 0.25 g of azobisisobutyronitrile as a polymerization initiator was added thereto, and the inner temperature was maintained at 95° C. for 15 minutes, followed by cooling to room temperature, to obtain a partially polymerized product.

To 1,000 g of the partially polymerized product were added and dissolved therein under thorough stirring 4 g of lauroyl peroxide, 3.0 g of t-dodecyl mercaptan as a molecular weight controller, 0.2 g of "JP-504" (trade name, produced by Johoku Kagaku Co.) as a peeling agent, 0.1 g of "Mark 329" (trade name: produced by Adeka Argus Co.) as a stabilizer, 0.2 g of "Tinuvin P" (trade name: produced by Ciba Geigy AG) as an UV-absorber and 1 g of stearic acid monoglyceride as a mold release agent. This partially polymerized mixture was poured into a mold comprising a cell formed of two tempered glass plates place at a distance of 3 mm through an intermediary polyvinyl chloride gasket, which cell was equipped with a thermocouple, and curing by polymerization was conducted in a water bath at 80° C. Thirty minutes after confirmation of the time from immersion in the water bath until the inner temperature reaches its peak, the mold was taken out from the water bath and subjected to heat treatment in an air-heated furnace at 130° C. for 2 hours. After cooling, the glass plates were removed to obtain a resin plate with a plate thickness of about 3 mm. The plate was cut and crushed into pellets of about 3 to 4 mm.

                  TABLE 19                                                         ______________________________________                                                Composition of monomeric mixture (g)                                           Methyl                                                                         metha-  α-Methyl     Maleic                                              crylate styrene  Styrene   anhydride                                           (MMA)   (α-MeSt)                                                                          (St)      (MAH)                                        ______________________________________                                         Example 28                                                                              700        50      125     125                                        Example 29                                                                              700        50      150     100                                        Example 30                                                                              700       100       50     150                                        Example 31                                                                              700       150       50     100                                        Example 32                                                                              765        35      100     100                                        Comparative                                                                             150       250      300     300                                        example 24                                                                     ______________________________________                                    

These pellets were blended with the same methacrylic polymer as used in Example 25 at weight ratios as indicated in Table 20 molded into pellets by means of a 40 mm φ vent type monoaxial extruder (extrusion temperature: 265° C.). These pellets were injection molded under the conditions shown below, and evaluated for their physical properties to obtain the results shown in Table 21.

                  TABLE 20                                                         ______________________________________                                                Copolymer of MMA/α-                                                                     Methacrylic polymer                                             MeSt/St/MAH copolymer                                                                         (Acrypet VH) (g)                                         ______________________________________                                         Example 28                                                                              750              250                                                  Example 29                                                                              600              400                                                  Example 30                                                                              400              600                                                  Example 31                                                                              300              700                                                  Example 32                                                                              850              150                                                  Comparative                                                                             750              250                                                  example 24                                                                     ______________________________________                                    

                                      TABLE 21                                     __________________________________________________________________________                        Total                                                                     Tensile                                                                             light                                                       MFR           strength                                                                            trans-    Boiling                                                                             Weather-                                                                            Solvent                                 (g/10     H.D.T.                                                                             (Kg/ mit-  Color*                                                                             resis-                                                                              ing resis-                                                                          resistance                              min.)     (°C.)                                                                       cm.sup.2)                                                                           tance (%)                                                                            tone                                                                               tance                                                                               tance**                                                                             (sec.)                                  __________________________________________________________________________     Example 28                                                                           7.6 115 790  92    color-                                                                             not whit-                                                                           no   160                                                              less                                                                               ened change                                                                trans-                                                                         parent                                                Example 29                                                                           8.2 112 760  92    color-                                                                             not whit-                                                                           no   150                                                              less                                                                               ened change                                                                trans-                                                                         parent                                                Example 30                                                                           7.0 117 750  92    color-                                                                             not whit-                                                                           no   170                                                              less                                                                               ened change                                                                trans-                                                                         parent                                                Example 31                                                                           8.5 117 740  92    color-                                                                             not whit-                                                                           no   150                                                              less                                                                               ened change                                                                trans-                                                                         parent                                                Example 32                                                                           6.0 114 750  92    color-                                                                             not whit-                                                                           slight-                                                                             120                                                              less                                                                               ened ly pale                                                               trans-   yellow                                                                parent                                                Compara-                                                                             7.0 140 500  opaque                                                                               opaque                                                                             whitened                                                                            craze                                                                                45                                     tive ex-                          gener-                                       ample 24                          ated                                         __________________________________________________________________________      *Color tone of injection molded plate                                          **Accelerated exposure test, 1100 hours                                  

EXAMPLES 33-35, COMPARATIVE EXAMPLE 25

A resin plate with a thickness of 3 mm was prepared according to entirely the same procedure as in Example 23 except for using a monomeric mixture comprising 665 g of methyl methacrylate, 55 g of α-methylstyrene, 140 g of p-methylstyrene and 140 g of maleic anhydride and changing the amount of t-dodecyl mercaptan during partial polymerization to 4.0 g. The plate was cut, crushed and then blended with "Acrypet VH" (trade name, produced by Mitsubishi Rayon Co.) at the proportions (parts by weight) as indicated in Table 22. The blended products were molded into pellets by means a biaxial extruder (temperature 265° C.).

                  TABLE 22                                                         ______________________________________                                                Copolymer of                                                                              Methacrylic                                                         MMA/α-MeSt/p-                                                                       polymer      MMA-BA*                                                MeSt/MAH   (Acrypet VH) (g)                                                                            copolymer                                       ______________________________________                                         Comparative                                                                             500                       500                                         example 25                                                                     Example 33                                                                              750          250                                                      Example 34                                                                              500          500                                                      Example 35                                                                              250          750                                                      ______________________________________                                          *Methyl methacrylatebutyl acrylate copolymer (Weight ratio = 50:50)      

These pellets were injection molded similarly as in Example 23 and the resultant test strips were evaluated to obtain the results as shown in Table 23.

                  TABLE 23                                                         ______________________________________                                                  Compara-                                                              Evaluation                                                                              tive                                                                  item     example 25                                                                               Example 33                                                                               Example 34                                                                             Example 35                                ______________________________________                                         H.D.T. (°C.)                                                                     90        122       116     109                                       Total light                                                                             60        92        92      92                                        transmit-                                                                      tance (%)                                                                      Tensile  700       740       760     780                                       strength                                                                       (Kg/cm.sup.2)                                                                  Elongation                                                                              4.2       6.6       4.3     3.9                                       (%)                                                                            Color tone                                                                              semi-     color-    color-  color-                                    of injec-                                                                               trans-    less      less    less                                      tion molded                                                                             parent    trans-    trans-  trans-                                    plate              parent    parent  parent                                    Weathering                                                                              no        no        no      no                                        resistance                                                                              change    change    change  change                                    (acceler-                                                                      ated exposure                                                                  test, 1100                                                                     hours)                                                                         Boiling  not       not       not     not                                       resistance                                                                              whitened  whitened  whitened                                                                               whitened                                  Solvent  140       180       130     110                                       resistance                                                                     (sec.)                                                                         ______________________________________                                     

We claim:
 1. A heat-resistant transparent methacrylic resin composition which comprises 5 to 95% by weight of a copolymer [I] obtained by (A) copolymerizing 40 to 98% by weight of methyl methacrylate, 1 to 25% by weight of an aromatic vinyl compound and 1 to 25% by weight of maleic anhydride or (B) copolymerizing 40 to 97% by weight of methyl methacrylate, 1 to 20% by weight of an alpha-methyl styrene, 1 to 20% by weight of styrene or vinyl toluene and 1 to 20% by weight of maleic anhydride and 95 to 5% by weight of polymer [II] obtained by copolymerizing 80 to 100% by weight of methyl methacrylate and 0 to 20% by weight of at least one other copolymerizable ethylenic monomer.
 2. A heat-resistant methacrylic resin composition according to claim 1, wherein the aromatic vinyl compound is selected from the group consisting of α-methylstyrene, styrene and vinyltoluene.
 3. A heat-resistant methacrylic resin composition according to claim 1, wherein the copolymer [I] is a copolymer obtained by copolymerizing 50 to 98% by weight of methyl methacrylate, 1 to 25% by weight of styrene or vinyltoluene and 1 to 25% by weight of maleic anhydride.
 4. A heat-resistant methacrylic resin composition according to claim 1, wherein the copolymer [I] is a copolymer obtained by copolymerizing 50 to 98% by weight of methyl methacrylate, 1 to 25% by weight of α-methylstyrene and 1 to 25% by weight of maleic anhydride.
 5. A heat-resistant methacrylic resin composition according to claim 1, wherein the copolymer [I] is a copolymer obtained by copolymerizing 40 to 97% by weight of methyl methacrylate, 1 to 20% by weight of styrene or vinyl toluene, 1 to 20% by weight of α-methylstyrene and 1 to 20% by weight of maleic anhydride.
 6. A heat-resistant methacrylic resin composition according to claim 1, wherein the other copolymerizable ethylenic monomer is at least one selected from the group consisting of an alkyl acrylate of which the alkyl group has 1 to 12 carbon atoms, an alkyl methacrylate of which the alkyl group has 2 to 12 carbon atoms, cyclohexyl methacrylate, styrene and acrylonitrile.
 7. A heat-resistant methacrylic resin composition according to claim 1, consisting of not less than 10 and less than 90% by weight of the copolymer [I] and more than 10 and not more than 90% by weight of the copolymer [II].
 8. A heat-resistant methacrylic resin composition according to claim 7, consisting of 15 to 85% by weight of the copolymer [I] and 85 to 15% by weight of the copolymer [II].
 9. A heat-resistant methacrylic resin composition according to claim 8, consisting of 20 to 80% by weight of the copolymer [I] and 80 to 20% by weight of the copolymer [II].
 10. A heat-resistant methacrylic resin composition according to claim 1, having a heat distortion temperature of 105° C. or higher as measured according to the method of ASTM D-648.
 11. A heat-resistant methacrylic resin composition according to claim 10, having a heat distortion temperature of 110° C. or higher as measured according to the method of ASTM D-648.
 12. A heat-resistant methacrylic resin composition according to claim 11, having a heat distortion temperature of 115° C. or higher as measured according to the method of ASTM D-648.
 13. A heat-resistant methacrylic resin composition according to claim 3, wherein the copolymer [I] is a copolymer obtained by copolymerizing 65 to 90% by weight of methyl methacrylate, 5 to 20% by weight of styrene or vinyltoluene and 5 to 15% by weight of maleic anhydride.
 14. A heat-resistant methacrylic resin composition according to claim 4, wherein the copolymer [I] is a copolymer obtained by copolymerizing 65 to 90% by weight of methyl methacrylate, 5 to 18% by weight of α-methylstyrene and 5 to 17% by weight of maleic anhydride.
 15. A heat-resistant methacrylic resin composition according to claim 5, wherein the copolymer [I] is a copolymer obtained by copolymerizing 60 to 90% by weight of methyl methacrylate, 1 to 10% by weight of α-methylstyrene, 5 to 15% by weight of styrene or vinyltoluene and 4 to 15% by weight of maleic anhydride.
 16. A heat-resistant methacrylic resin composition according to claim 3, wherein the ratio of α/γ (where α is a mole number of styrene or vinyltoluene and γ is a mole number of maleic anhydride) is 0.9 to 1.7.
 17. A heat-resistant methacrylic resin composition according to claim 4, wherein the ratio of β/γ (where β is a mole number of α-methylstyrene and γ is a mole number of maleic anhydride) is 0.9 to 1.7.
 18. A heat-resistant methacrylic resin composition according to claim 5, wherein the ratio of (α+β)/γ (where α is a mole number of styrene or vinyltoluene, β is a mole number of α-methylstyrene and γ is a mole number of maleic anhydride) is 0.9 to 1.7. 